Field of the Invention
The present invention relates to a method and apparatus for rinsing and drying of a substrate in semiconductor manufacturing. More particularly, it relates to an improved method for rinsing and drying a substrate, in which defect counts are reduced.
Description of Related Art
A rinsing and drying step is commonly used in many processes in semiconductor manufacturing. In photolithography, this step is used after development of photoresist, to rinse the developer along with developed photoresist, and dry the substrate prior to removal from the processing tool. These steps are also used in other wet processing of substrates, for example, following substrate wet cleaning, or following electrochemical deposition.
In a typical rinse and dry step, the substrate is mounted on a spin chuck and rotated at a set rotation speed. Rinse liquid is dispensed from a nozzle, or plurality of nozzles onto the substrate, the rinse liquid displacing the contaminant that needs to be removed from the substrate. The contaminant may be, for example, a developer solution, cleaning solution, or electrolyte for electrochemical deposition. In a typical process, the rinse solution is introduced at the center of the substrate, initially radially displacing the contaminant from the center of the substrate. The radial displacement of the contaminant along with the rinse liquid is assisted by substrate rotation and by subsequently starting a flow of purge gas, where the flow of purge gas is used to remove the last droplets and traces of contaminant and rinse liquid from the substrate. The rinse liquid dispense nozzle and the purge gas nozzle, or plurality of nozzles, are typically moved across the surface of the substrate in a direction generally outwards from the center of the substrate, towards the substrate edge, leaving a cleaned and dried portion behind. The instantaneous boundary between the still-wet and dry portions of the substrate is defined by a circular rinse liquid meniscus. As the nozzles are moved radially outwards, so does the meniscus. Once the meniscus reaches the edge of the substrate, the entirety of the substrate has been rinsed and dried, and it can be removed from the spin chuck and processing tool for subsequent processing steps.
In semiconductor processing, the desire exists to increase process throughput, i.e. the number of substrates processed in a set amount of time. This desire to increase throughput leads to the use of aggressive processing conditions (i.e., substrate rotation speeds, rinse liquid and purge gas flows and velocities, nozzle movement velocities, etc.) which may lead under certain conditions to the disruption of the meniscus by the purge gas flow, or splashing of still-adhered rinse liquid and contaminant from the wet portion of the substrate to the dry portion of the substrate, both of which can lead to increased device defect counts and reduced processing yield. Under typical processing conditions, the defect count density increases with radius and is highest at the substrate periphery. Improvements are therefore needed to address these high defect counts, particularly at the substrate periphery, while maintaining low processing times and thus high process throughputs.
Specifically, the need exists for a method of optimizing the rinsing and drying process so as to maximize throughput without causing meniscus disruption and splashing, and thus increased defect counts.